        ([repl-env env form]
          (self repl-env env form nil))
        ([repl-env env [_ [quote ns-name] :as form] _]
+         ;; guard against craziness like '5 which wreaks havoc
+         (when-not (and (= quote 'quote) (symbol? ns-name))
+           (throw (IllegalArgumentException. "Argument to in-ns must be a symbol.")))
          (when-not (ana/get-namespace ns-name)
            (swap! env/*compiler* assoc-in [::ana/namespaces ns-name] {:name ns-name})
            (-evaluate repl-env "<cljs repl>" 1


              (and (seq? form) (is-special-fn? (first form)))
              (do
                ((get special-fns (first form))
                  repl-env env form opts)
                (newline)
                (recur))


            [cljs.source-map :as sm]
            [clojure.tools.reader :as reader]
            [clojure.tools.reader.reader-types :as readers]
            [cljs.util :as util]
            [clojure.stacktrace :as trace])
  (:import [java.io File PushbackReader]
           [javax.xml.bind DatatypeConverter]))

